The present application relates generally to the field of fluid control valves. The present application relates more specifically to the field of thermostatic control valves.
Fluid control valves for plumbing fixtures (e.g., shower control valves) often include a control mechanism to prevent the sudden change in temperature of the water. In the classic example, flushing a toilet may reduce the supply of cold water, thereby causing a sudden increase in temperature of a nearby shower. One version of such control mechanism is a pressure balance unit, which uses a diaphragm or shuttle to balance the pressure between parallel but separate flows of hot and cold water. Another version of such control mechanism is a thermostatic valve, which uses a thermostat to control the flow of hot and cold water.
A typical thermostatic valve has a cold water inlet, a hot water inlet, and a mixed water outlet. The mixed water flows over a thermostat, the expansion and contraction of which causes a shuttle attached to the thermostat to move relative to the hot and cold water inlets, thereby controlling the proportion of hot and cold water flowing through the valve, and thereby regulating the temperature of the outgoing mixed water.
In a typical thermostatic valve, the shuttle needs to seal between the hot and cold water sides, while being able to move freely relative to the hot and cold water inlets. This creates competing interests between low friction and good sealing. Furthermore, as water flows around and through the shuttle, various pressure gradients are set up around the shuttle, thereby making the shuttle susceptible to resonant frequencies, which may result in whistling or other noises that may be annoying to a user. The pressure gradients may further cause seals to become dislodged from the shuttle. Accordingly, shuttles tend to be relatively large, in turn causing relatively large valve cartridges, which, in turn, lead to relatively large valve bodies, all of which increase the cost of the valve. Thus, there is a need for an improved thermostatic valve cartridge.